Touch screens as user interfaces are enjoying widespread commercial success, and are implemented in numerous devices. These devices include, for example, cellular telephones, tablet computer devices, digital music players, and point of sale equipment, just to name a few. The ubiquitous presence and user familiarity of touch screens make this technology a natural candidate for use in aircraft cockpit displays. However, a vast majority of touch screen user interfaces are implemented using capacitive touch detection systems. These systems, when implemented in cockpit displays, can exhibit certain undesirable performance issues. For example, capacitive touch detection systems can be difficult to use when a user is wearing gloves. These systems are also susceptible to false touch detection when exposed to fluid spills or condensing moisture on the touch sensor surface.
Capacitive touch detection systems rely on an applied electric field that is scanned to detect changes in the field caused by a touch event. Thus, if the electric field strength is increased, it becomes feasible to use gloves to activate a touch event. Moreover, by adjusting the field strength, it is also possible to change the sensitivity to any liquids that may be on the sensor surface. Unfortunately, in the context of commercial aircraft, the relatively strong electric field that may be needed to implement gloved operation or to overcome the impact of fluids can increase radiated emissions from the touch sensor, thereby complicating qualification and certification activities.
Hence, there is a need for a capacitive touch detection system and method that implements touch sensitivity control without adjustability without unduly increasing radiated emissions therefrom. The present invention addresses at least this need.